PWS is a genetic condition that affects many parts of the body. Patients with this condition are generally obese, have low muscle tone and mental ability, and produce few or no sex-related hormones. They also tend to have neurobehavioral and psychiatric problems, including abnormal repetitive behaviors.

PWS is caused by the absence of a region of chromosome number 15, called 15q11.2-q13, contributed by the father. Most PWS cases (65% to 75%) are caused by the deletion of genes in this region of the chromosome, but other genetic abnormalities also cause PWS. Although PWS has been well characterized, the syndrome’s genetic causes have not been extensively studied.

To better understand the genetics of PWS, researchers supported by the Intellectual and Developmental Disabilities Branch examined gene deletion in PWS patients. They discovered that 8% of patients had deletions that had not been previously identified in PWS patients. Among the newly identified PWS deletions were deletions of chromosome region 15q13.3. In other studies, deletions of this region have been linked to an increased risk of seizures and intellectual disability, but this is the first study to report deletions of this region in PWS patients.

Patients with the newly identified deletions had clinical signs distinct from those of patients with other genetics of the disease, suggesting that certain clinical signs could be used to identify the underlying genetics of some cases (PMID: 22045295).